McCulloch Bar Modification-medium to large

[Tzed250]

I have had a couple of 28" NOS McCulloch sprocket nose bars hanging around for a while. I decided that I would modify one to fit my SP125C so that I could do some work to my 36" bar. The 28" bar was originally made to fit the saws that include the 10-10, PM700, 610, etc. The slot on that bar is .320" wide (5/16" nominal). The slot on the large mount bars is .390" (3/8" nominal). A trip to the Bridgeport was in order.



After using two heel clamps to secure the bar to the table, I used an edge finder to locate the center of the slot.

<a href="http://www.flickr.com/photos/41385771@N03/5316769477/" title="Untitled by zweitakt250, on Flickr"><img src="http://farm6.static.flickr.com/5044/5316769477_4df62e077d_z.jpg" width="640" height="480" alt="" /></a>




The tool that I used was a .375" 4-flute solid carbide end mill. Bar steel is very tough. It can be cut with high speed steel, but your surface speed must be much lower than with carbide. One pass down the center, then a .007" pass up each side set the width at .39"

<a href="http://www.flickr.com/photos/41385771@N03/5316761451/" title="Bar Slot by zweitakt250, on Flickr"><img src="http://farm6.static.flickr.com/5084/5316761451_f6a6152338_z.jpg" width="640" height="480" alt="Bar Slot" /></a>




Because the tail on the smaller bar is more narrow than the large bar I had to modify a set of spacer plates so that the chain rivets would not drag on the larger bar plates. After scribing the profile from the small bar, the plates were shaped on a belt sander. You can see the size difference between the stock plate and the narrowed plate in the pictures.

<a href="http://www.flickr.com/photos/41385771@N03/5317360474/" title="Spacer plate by zweitakt250, on Flickr"><img src="http://farm6.static.flickr.com/5121/5317360474_5eaa269131_z.jpg" width="640" height="480" alt="Spacer plate" /></a>




I ordered a new square ground Oregon chain, along with an 8 tooth sprocket, from Bailey's and that gave me everything I needed. It all went together without a hitch.

<a href="http://www.flickr.com/photos/41385771@N03/5316739405/" title="SP newbar by zweitakt250, on Flickr"><img src="http://farm6.static.flickr.com/5282/5316739405_526bff9747_z.jpg" width="832" height="553" alt="SP newbar" /></a>



Now, if Spring will just get here...


.

 

[rwoods]

Very nice work. Thanks for posting it. Ron

 

[pioneerguy600]

Nice work John,.. thanks for posting the picts, for some picts, tell a thousand words.
Pioneerguy600

 

[Tzed250]

Thanks Jerry. I know that the large mount McCulloch bars become more scarce every day. This might give a leg up to someone trying to get one of the big Mac's going with the medium bar. I like to make pictures, so that part is easy for me...

 

[Bob Wright]

Nice job. Its nice to have the right tools and machines...Bob

 

[boda65]

I did much the same thing with a large mount Husky bar to fit my SP105. I trashed my mill cutter. I thought only the rails were hardened, but much to my chagrin the whole dang bar was tougher'n Kelsey's nuts. I also had to grind in oil passages from the adjuster holes to the chain groove. There are so many old Macs with this bar mount I would think someone would still make them.
Jim

 

[willysmn]

Mac bar mods

Very nice work and photography. I also did not realize that ihe interior of the bar was hard too.

 

[Man of $tihl]

thats a fine job. with that 28''bar it makes that 125 more usable. and lighter.

 

[Brian13]

Thanks for posting the pics. Very useful information!!!

 

[Tzed250]

Very nice work and photography. I also did not realize that ihe interior of the bar was hard too.

The slot of the bar isn't "hard" as a machinist would call it, it is "tough". If a file will cut it, then a high speed steel tool will cut it. You need to limit yourself to about 35SFM though, which for a .375 cutter is 357 RPM. If the whole bar was hard, it would break.

.

 

[Jacob J.]

Hey John- very cool modification, great work. Sometimes it takes some elbow grease to keep these old monsters running, but it's well worth it.

 

[heimannm]

I have modified a couple of 10/600 Series bars to fit my large mount McCulloch's with nothing more than a couple of files (large flat and a round to dress up the ends). I think each one took 30-40 minutes of filing, flipping, checking to get them to fit.

There is a McCulloch part number (92020) for the bar spacers that Tzed had to make. As of last week I got the last ones that Bob Johnson had, but more may show up.

Mark

 

[jerryw66]

Nice job and pics, Mark. I've modified a windsor bar a few times, pretty much in the same fashion, here's the sheet that comes with new spacer plates. I've been thinking of having one of my laser cutting buddies make a batch of em. After the first one, they don't cost too much.

 

[Tzed250]

Hey John- very cool modification, great work. Sometimes it takes some elbow grease to keep these old monsters running, but it's well worth it.

The elbow grease lets me "connect" with the saw. You are so right...truly well worth it.

 

[1375619cm3]

i did the same thing for my 250 to wear its 31" bar with just a grinder and a file easy and very useful modification thanks for sharing the pictures of the spacers i need to make some of those yet.